AI in Computer Games. AI in Computer Games. Goals. Game A(I?) History Game categories

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1 AI in Computer Games why, where and how AI in Computer Games Goals Game categories History Common issues and methods Issues in various game categories Goals Games are entertainment! Important that things behave naturally not necessarily perfect "things" are not always creatures Follow (the game's) natural laws and avoid cheating Characters should be aware Game A(I?) Academic AI is usually concerned with making rational decisions Searching for the optimal solution Game AI is more often about Artificial Life Believable behaviour including realistic physics Game balancing challenging, but not unbeatable opponents Game categories Role Playing Games (RPG, MMORPG) First Person (Third Person) Shooters (FPS/TPS) Real Time Strategy (RTS) games Sports games Simulation games Adventure games Classic strategy games Fighting games... History 's First computer games 1970's SpaceWar (for two human players) (1962) Board games (e.g. chess) against the machine Pong (first public computer game?) (1972) First computer controlled opponent in arcade games Space Invaders Space Invaders (1978) Predefined patterns "AI" takes 1-2% of CPU Pong Chess 1

2 1980's Pac-Man (1980) opponents with personality A computer beats a master chess player (1983) Tekken 3 First fighting games Adventure games Dungeon, Zork,... First MORPG (MUD) Pac Man 1990's FPS and RTS games Games about/with evolution and learning (Creatures, Black&White) Deep Blue beats Kasparov (1997) Graphic cards take the load off the CPU AI takes 10-35% of CPU Doom Dune 2 Black & White Computer games is a big industry Games sell for about 25 billion USD per year Market grows with 16% per year A game project: 2 years, 8-15 million USD Less cheating in AI Characters are more aware Characters collaborate better Focus shift from graphics towards AI Typical Game AI topics Strategical/tactical decisions Against or with you Search for best counter action adaptivity Simulation of natural behaviour for animation (e.g. bird flocks) Shortest path problems Some methods Minimax logic games, search for best counter action Finite State Machines (FSM) Behaviour A* For shortest path problems Particle methods Simulation of flocks, smoke, water, grass,... Smart terrain Minimax (counter actions) MAX MIN 7 MAX Variants: α-β-pruning and expectimax 2

3 Distance from S + estimated distance to G A* Finite State Machines Pacman ghost (red) 3+8=11 2+7=9 3+6=9 4+5=9 2+7=9 1+6=7 2+5=7 3+4=7 S 1+4=5 1+6=7 2+3=5 G 2+5=7 3+6=9 Reinforcement Learning 4+5=9 5+4=9 6+3=9 7+2=9 8+1=9 Best shortest Civilization III Smart terrain Stor knowledge in objects instead of in the characters Easier to know what is relevant Easier to add new objects later drink me! not thirsty, warm Thoughts on learning Game characters are short lived Learning requires many attempts Keep it simple! Probabilistic methods (Menace) Evoutionary methods Neural networks Invented by Will Wright (Sims) genetic algorithms in game development, but not in the game 3

4 Thoughts on learning AI in various game types Board games Role playing games Strategy games Platform and sports games Racing games Board games Discrete time / turn based Often deterministic AI is in the opponent AI goal is non-typical (for games) usually strives for optimality Tree search Library Reinforcement learning Chess Role Playing and Adventure AI in enemies, bosses, party members and other NPCs,... Scripting, FSMs, Messaging Role Playing Combat combat oriented games are simpler to make Conversations (grammar machines) Quest generators Towns The Elder Scrolls IV: Oblivion Town behaviour Town behaviour Need-based system Needs (e.g. hunger, business,...) Actions (e.g. eating, trading,...) "Need pathfinding" Problems Finding people Unwanted interaction between NPCs The Elder Scrolls III: Morrowind 4

5 Strategy games Strategy games AI heavy (on both sides) Shortest path problems Strategical decisions Tactical decisions Town building and resource management planning Indigenous life Reconnaissance (fog-of-war) Diplomacy Know thy enemy (observe and adapt) Civilization III Civilization III Action games (FPS, TPS) Action games (FPS, TPS) Enemies Weapons Cooperative agents Attention requires perception requires a good physics engine Pathfinding Spatial reasoning Anticipation Half Life 2 Thief 3: Deadly Shadows Platforms and sports Platforms and sports Platform games Since 1996 (Mario 64) in 3D Camera problems Sports games Camera problems (harder) Cooperation Game balance can be difficult Learning Prince of Persia Prince of Persia: The Two Thrones 5

6 Racing games Racing games Track AI Traffic (including pedestrians) Physics Tuning NPCs and vehicle parameters Genetic algorithms Particle swarm optimization Forza Motorsport Conclusion Making realistic games requires more than good graphics Computer controlled characters must behave Naturally Reasonably intelligent, without cheating! Graphics has dedicated hardware More processing power avilable to AI In the future Dedicated AI cards? Multi core processors Knowledge transfer from games to robotics Robocup (Aibo league) 6